The goalkeeper urged the Basques to move on as quickly as possible after failing in their brave bid to end the club's wait for a first continental trophy
The Basques had high hopes of ending their wait for a first continental title after overcoming Manchester United and Schalke on their way to Bucharest, but they were outgunned by their Liga rivals in the tournament decider, succumbing to two first-half goals from Radamel Falcao and a third from Diego late on.
Iraizoz was unable to hide his own disappointment at the full-time whistle but he insisted afterwards that the players simply have to put the game behind them if they are to have any chance of upsetting Barca at the Vicente Calderon on May 25.
"In 15 days we have another final," the goalkeeper told reporters in the Romanian capital. "We have made it to two finals, which is something few teams do, and although tonight it is difficult, we now have to grit our teeth and, with the support of our fans, hopefully re-emerge in the same way Athletic have done many times before.
"We must go on. We must believe in the work that is being done and be proud of the way in which we got here.
"What we have to do now is to stick together; to be united. We know that we have another chance and we must cling to that now."
Before they can fully focus on the Blaugrana, Athletic must first complete their league campaign with a trip to Valencia on Sunday to take on Levante.